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1. Field of the Invention
The present invention relates to floating marine platforms. More particularly, the present invention relates to a novel multiple buoy platform that supports a platform with a plurality of buoys and wherein a specially configured multiple device support enables replacement of one device while the other supports the platform.
2. General Background of the Invention
Many types of marine platforms have been designed, patented and used commercially. Marine platforms typically take the form of either fixed platforms that include a large underwater support structure or xe2x80x9cjacketxe2x80x9d or a floating platform having a submersible support. Sometimes these platforms are called semi-submersible rigs.
Jack-up barges are another type of platform that can be used in an offshore marine environment for drilling/production. Jack-up barges have a barge with long legs that can be powered up for travel and powered down to elevate the barge above the water.
Other types of platforms for deep water (1500 feet or deeper) have been patented. The September 2000 issue of Offshore Magazine shows many floating offshore platforms for use in deep water drilling and/or production. Some of the following patents relate to offshore platforms, some of which are buoy type offshore platforms, all of which are hereby incorporated herein by reference. Other patents have issued that relate in general to floating structures, and include some patents disclosing structures that would not be suitable for use in oil and gas well drilling and/or production.
One of the problems with the spar type construction is that the single spar must be enormous and thus very expensive to manufacture, transport, and install if it is supporting a drilling rig or production platform weighing between 5,000 and 40,000 tons, for example (or even a package of between 500-100,000 tons).
The present invention provides an improved offshore marine platform that can be used for drilling for oil and/or gas or in the production of oil and gas from an offshore environment. Such drilling and/or production facilities typically weigh between 500-100,000 tons, more commonly between 3000-50,000 tons.
The apparatus of the present invention thus provides a marine platform that is comprised of a plurality of spaced apart buoys, the platform having a periphery that includes a plurality of attachment positions, one attachment position for each buoy.
Each of the buoys will move due to current and/or wind and/or wave action or due to other dynamic marine environmental factors. xe2x80x9cArticulating connectionxe2x80x9d as used herein should be understood to mean any connection or joint that connects a buoy to the superstructure, transmits axial and shear forces, and allows the support buoy(s) to move relative to the superstructure without separation, and wherein the bending moment transferred to the superstructure from one of the so connected buoys or from multiple of the so connected buoys is reduced, minimized or substantially eliminated. xe2x80x9cArticulating connectionxe2x80x9d is a joint movably connecting a buoy to a superstructure wherein axial and tangential forces are substantially transmitted, however, transfer of bending moment is substantially reduced or minimized through the joint allowing relative movement between the buoy and the superstructure.
A connection (which can be an articulating connection) connects each buoy to the platform at a respective attachment position, the connection allowing for sea state induced buoy motions while minimizing effects on the platform.
The apparatus of the present invention provides a marine platform that can further comprise a mooring extending from a plurality of the buoys for holding the platform and buoys to a desired location.
In a preferred embodiment, the present invention provides a marine platform wherein each of the articulating connections includes corresponding concave and convex engaging portions. In another embodiment, a universal type joint is disclosed.
In another embodiment a marine platform has buoys with convex articulating portions and the platform has correspondingly shaped concave articulating portions.
In a preferred embodiment, each buoy can be provided with a concave articulating portion and the platform with a convex articulating portion.
In a preferred embodiment, each buoy has a height and a diameter. In a preferred embodiment, the height is much greater than the diameter for each of the buoys.
In the preferred embodiment, each buoy is preferably between 25 and 100 feet in diameter.
The apparatus of the present invention preferably provides a plurality of buoys, wherein each buoy is between about 100 and 500 feet in height.
The buoys can be of a generally uniform diameter along a majority of the buoy. However, each buoy can have a variable diameter in an alternate embodiment.
In a preferred embodiment, each buoy is generally cylindrically shaped. However, each buoy can be provided with simply an upper end portion that is generally cylindrically shaped.
In a preferred embodiment, there are at least three buoys and at least three attachment positions, preferably four buoys and four attachment positions.
In a preferred embodiment, each articulated connection is preferably hemispherically shaped for the upper end portion of each buoy and there is a correspondingly concavely shaped receptacle on the platform that fits the surface of each hemispherically shaped upper end portion.
The connection can also be in the form of a universal joint. In an additional embodiment, the connection can be in the form of first and second devices that provide xe2x80x9cbackupxe2x80x9d or redundancy that enables one device to be serviced while the other supports the platform. In this embodiment, a first universal joint preferably carries load between the platform and each buoy over the long period of time. In the event that the first device must be replaced or serviced, a jacking arrangement loads the other device so that the first device does not carry load and can be removed.
The devices can include an inner device and an outer device. The xe2x80x9cdevicesxe2x80x9d can be articulating devices such as universal joints.
In a preferred embodiment, the platform is comprised of a trussed deck. The trussed deck preferably has lower horizontal members, upper horizontal members and a plurality of inclined members spanning between the upper and lower horizontal members, and wherein the attachment positions are next to the lower horizontal member.
In a preferred embodiment, the apparatus supports an oil and gas well drilling and/or production platform weighing between 500 and 100,000 tons, more particularly, weighing between 3,000 tons and 50,000.
The apparatus of the present invention uses articulating connections between the submerged portion of the buoy and the superstructure to minimize or reduce topside, wave induced motions during the structural life of the apparatus.
The apparatus of the present invention thus enables smaller, multiple hull components to be used to support the superstructure than a single column or single buoy floater.
With the present invention, the topside angular motion is reduced and is less than the topside angular motion of a single column floater of comparable weight.
With the present invention, there is substantially no bending moment or minimum bending moment transferred between each buoy and the structure being supported. The present invention thus minimizes or substantially eliminates moment transfer at the articulating connection that is formed between each buoy and the structure being supported. The buoys are thus substantially free to move in any direction relative to the supported structure or load excepting motion that would separate a buoy from the supported structure.
The present invention has particular utility in the supporting of oil and gas well drilling facilities and oil and gas well drilling production facilities. The apparatus of the present invention has particular utility in very deep water, for example, in excess of 1500 feet.
The present invention also has particular utility in tropical environments (for example West Africa and Brazil) wherein the environment produces long period swell action.